Motor-driven hand tool



y 1950 M. OSCHWALD 2,506,736

' MOTOR-DRIVEN HAND TOOL Original Filed April 1, 1947 2 Sheets-Sheet l I N VEN TOR.

fig-Q 0M y 1950 M. OSCHWALD 2,506,736

MOTOR-DRIVEN HAND TOOL Original Filed April 1, 1947 2 Sheets-Sheet 2 Patented May 9,

MOTOR-DRIVEN HAND 'rooi.

Max Oschwald, Zuchwil, Switzerland, assignor to Scintilla A-G., Solothurn, Switzerland, a corporation of Switzerland Original application April 1, 1947, Serial No. 738,660. Divided and this application July 31, 1948, Serial No. 41,786. In Switzerland February 15, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires February 15, 1965 6 Claims. 1

This application is a division of my copending application for a patent in the United States, Serial No. 738,660 filed April 1, 1947, and which issued as Patent No. 2,501,631 on March 21, 1950.

This invention relates to motor-driven tools designated to be moved by hand, and more especially to motor-driven reciprocating hand tools such as saws, cutters, files and the like.

It is an object of the invention to provide a light and handy tool permitting to operate on work pieces that are too bulky to be worked on a large machine, such as large plywood panels or lumber boards, or which enables work to be performed in positions which are inaccessible for ordinary hand tools.

A further object of the invention is to provide a mechanism for converting the rotary motion of a motor into rectilinear reciprocatory motion while eliminating the vibrations generated by its reciprocating masses which work at frequencies of at least 3000 power cycles per minute.

In order that the invention may be more readily understood, I will now describe an embodiment thereof which is illustrated diagrammatically by way of example in the accompanying drawings, in which:

Fig. 1 is a perspective view of the tool as a whole; while Fig. 2 is an axial sectional view drawn to a larger scale.

Fig. 3 is a cross-section along the line 3-3 in Fig. 2, while Figs. 4 and 5 are perspective views of the two main motion transmitting and transforming gear parts, and

Figs. 6 and 7 are end views of these parts if combined, shown in two positions.

Figs. 8 to 12 are diagrams showing the main motion transmitting and transforming mechanism in different working positions.

The mechanism according to the invention converts the rotary motion of a motor shaft into the reciprocatory motion of a tool by operating a crank arm with a pin connected positively to a pinion driven by a rotary mechanism in such manner as to travel orbitally in a circular path around a fixed internal gear whose pitch circle diameter is twice that of the pinion. To achieve linear motion of the crank pin, it is essential that its eccentricity be equal to one-half of the pitch circle diameter of the pinion to which it is connected.

Perfect balancing of the masses is effected according to this invention by the combination of parts described hereinafter.

With reference to the drawings, in which I is a casing which also forms the handle of the tool,

while 2 is the electro motor and 3 is its shaft, 4 is a cylindrical crank element, loosely lodged in an eccentric boring 21 of a rotatable drum 5. A planet wheel 6 is located concentrically on one side and integral with the crank element 4, while a crank pin 1 projects from the other side of the crank element 4, this pin being arranged eccentrically in regard to the axis of the crank element 4 and planet wheel 6. An internal gear ring 8 is fixed to the gear case l3 by means of screws 9 concentrically with the axis of the rotatory drum 5. The planet wheel 6 meshes with and rolls in the fixed internal gear ring 8. The pitch circle diameter of this ring is equal to twice the pitch circle diameter of the planet wheel 6. The eccentricity of the crank pin 7 is equal to one-half of the pitch circle diameter of the planet wheel 6. The drum 5 is formed with an internal gear iii which meshes with a pinion ll fixed on the end of the motor shaft 3. The drum 5 is supported in ball bearings 12 mounted in the gear casing 13. The end cover 14, the gear case [3, and the motor casing I are held together by screws l5.

The reciprocating tool arm 16 is slidably mounted in the end cover I l and is imparted reciprccating movement by the crank pin 1 through the tool holder I! to which it is fastened.

In order to obtain a complete counterbalancing of the rotating mass of the planet Wheel 6, the reciprocating masses of the crank pin 7, the tool arm IB and tool holder ll with the saw l8 attached to it, the crank element 4 is formed with a deep recess I9 in one half of its cylindrical body in alignment with crank pin 'l'. The mass 28 presented by the other half of the cylindrical body forms the counterweight necessary for complete compensation of the various masses.

The cable 25 containing the leads extends to the motor through the rear bearing plate 22. A tumbler switch 23 permits switching on and 01f of the current with the tip of a finger of the hand clasping the instrument.

The planetary gear drive of the tool operates as follows:

Let us assume that K is the pitch circle of the stationary internal gear 8 fixed to the motor casing 1, 7c the pitch circle of the planet gear 6 rolling in the internal gear 8, and T the drum e, while the diameter of K is 2]: and the eccentricity of the crank pin 1 in regard to the center of the cylinder W l) is equal to the radius of the pitch circle 70.

When the drum '1 rotates in the direction of the arrow P1 (Fig. 8), the pitch circle ic rolls in the stationary pitch K whereby the cylinder W is rotated in the direction of the arrow P2 and at 3 the same time is carried along in the direction of the arrow P1 by the drum T. Now, if during rotation of the drum T the axis A, which forms the common center of the cylinder W and the pitch circle is, has covered for instance A; of a circle with respect to the axis B (Fig. 9), the

length of the are between the axes A and B amounts to A; of the circumference of pitch circle K, While the length of the arc of pitch circle k, which has rolled on it during the same period of time, amounts to ,4; of the circumference of this latter, because the difference between the two diameters is as 2:1. If, on the drum T rotating further, the length of the arc between the axes A and B becomes A; of the circumference oi pitch circle K, then the crank pin Z, with respect to the center of pitch circle K, starting from its point of contact with the two pitch circles, has covered revolution and has arrived at the center of the drum T (Fig. 19). No matter what may be the relative position of the members of this system, the center of the crank pin Z will always coincide with a point of intersection of the axis B and the pitch circle is, excepting only the case in which the axes enclose between them an angle of 9Q and the pitch circle k, while contacting the axis in the center of the drum T from one side or the other, does not intersect it (Fig. 10.).

The ratio between the angles a and p enclosed between the axes A and B or A and C, as well as between the respective lengths of the arcs of the pitch circles K and k is 1:2 at any value of a. The axis C constitutes an extension of the line connecting the centers of the pitch circle is and the crank pin Z. In every angular position of" the drum T the angle [3 is equal to 20., and therefore angle y is equal to 6.

Consequently, during all its movements the center of the crank pin Z travels on a straight line coinciding with the axis '3 I wish it to be understood that I do not desire to be limited to the details of construction shown and described for obvious modifications will occur'to a personskilled in the art.

I claim 1. In mechanism for converting rotary motion of a motor-driven shaft into rapid recipro catory motion of a saw blade or other tool, the combination of a driven shaft, a tool holder arranged for reciprocatory movement at an angle to the shaft axis and power-transmitting and motion conver'ting gearing comprising a gear case, a crank member operatively connected with said tool holder, a cylindrical body carrying said crank member in an eccentric position and a planet gear in centric position, a gear on said driven shaft and a rotatory drum arranged eccentrically to and operatively connected with, said shaft gear for rotation and forming an eccentric housing for said cylindrical body and also a stationary internal gear ring for engagement with said planet gear.

2. In mechanism for converting rotary motion of a motor-driven shaft into rapid reciprocatory motion of a saw blade or other tool, the combination of a driven shaft, a tool holder arranged for reciprocatory movement at an angle to the shaft axis and power-transmitting and motion-converting gearing comprising a gear case, a crank member operatively connected with said tool holder, an unbalanced cylindrical body carrying said crank member in an eccentric position and a planet gear in centric position, a gear on said driven shaft and a rotatory drum arranged cow centrically to and operatively connected with, said shaft gear for rotation and forming an eccentric honsing for said cylindrical body and also astationary internal gear ring for engagement with said planet gear.

3. In mechanism for converting rotary motion of a motor-driven shaft into rapid reciprocatory motion of a saw blade or other tool, the combination of a driven shaft, a tool holder arranged for reciprocatory movement at an angle to the shaft axis and power-transmitting and motionconverting gearing comprising a gear case, a crank member operatively connected with said tool holder, a cylindrical body carrying said crank member in an eccentric position and a planet gear in centric position, a gear on said driven shaft and an unbalanced drum arranged eccentrically to and operatively connected with, said sha t gear or o ati d fo min n eccent housi fo s c n cal bo y an rai es stationary internal gear ring for engagement with said planet gear.

4, In mechanism for converting rotary motion of a motor-driven shaft into rapid reciprocatory motion of a saw blade or other tool, the combination of a driven shaft, a tool holder arranged for reciprocatory movement at an angle to the shaft axis and power-transmitting and motionconverting gearing comprising gear case, a crank member operatively connected with said tool holder, an unbalanced cylindrical body carrying said crank member in an eccentric posi-. tion and a planet gear in centric position, a gear on said driven shaft and an unbalanced rotatory drum arranged eccentrically to and ollfiratively connected with said shaft gear for rotation and forming an eccentric housing for said cylindrical b y an al o a s ati a i ter al s a r g for ent th sa d pla sea 5. The mechanism of claim 12 in which a recess is formed in said cylindrical crank body to render it unbalanced.

'6, mechanism for converting rotary motion of a motor-driven shaft into rapid reciprocatory motion of a saw blade or othertool, the combination of a driven shaft, a tool holder arranged for reciprocatory movement at an angle to. the shaft axis and power-transmitting andmoltiom onv r i g ear n omp ising a, se l; ase, a crank member operatively connected with said tool holder, a cylindrical body carrying said crank memberin an eccentric position and a planet gear in centric position, a gear on said driven shaf and a rotatory drum arranged eccentrically and presenting internal gearing to said shaft gear, said cylindrical crank body being located for revolution in an eccentric boring of said drum, and a stationary internal gear ring, supported by said ear case, forming a race for said; planet gear.

nnrnannons err-en The fo lowin r f rences ar f record in th file o this a e t:

UNITED STATES PAIEN-IS Nell-fiber Name Gate.

2 082,4 De Br n r-i June 1,, 193,7. 505% K es et a1. July 274, 9.4.1

FOREIGN PATENTS Number Country lax-rte 6,044 Great Britain o f 19.15. 71,357. Norway ;Dec. 9, 1-946 

